Hello, Le 10/08/2014 13:55, Andre Vehreschild a écrit : > Hi, > > I am proposing another patch, this time to resolve PR60289. The issue in the > bug > reported is, that a code like: > > class(*), pointer :: P > allocate(character(20)::P) > > is rejected by trunk's gfortran compiler. ja...@gcc.gnu.org proposed a first > patch in the PR, which my patch extends. > > Motivation: Previously parsing of the type association to the unlimited > polymorphic variable P was not allowed and reported the error "Error: > Allocating p at (1) with type-spec requires the same character-length > parameter > as in the declaration", after the errorneous error report was fixed by > janus' patch, an ICE occured in trans-stmt.c's gfc_trans_allocate()-routine. > The ICE reported in PR60289 is something different and does not occur in trunk > anymore. The ICE reported now boils down to line 5056 in trans-stmt.c: > > tmp= al->expr->ts.u.cl->backend_decl; > > The dereferencing of ts.u's cl member is valid only, when ts.type is of > BT_CHARACTER. With al->expr being an unlimited polymorphic type, the > backend_decl is not available in cl. > > Although there is a backend_decl available in ts.u.derived, I was not able to > get it compatible for the fold_convert in the line following the assignment to > tmp: > > gfc_add_modify (&se.pre, tmp, fold_convert (TREE_TYPE(tmp), > se_sz.expr)); > > My current solution therefore is to execute those two statements only, when > ts.type is of BT_CHARACTER.
My knowledge of unlimited polymorphic types is limited, but I think that this is not correct. The new length of the string has to be stored somewhere. If you don't do that, for example the intrinsic len() function won't work. > > Can someone explain what the fold_convert is doing in that specific place? I > assume that it is checking for and ensuring some type compatibility. Is there > some documentation available, explaining this? Is something similar needed for > the unlimited polymorphic variable? Well, I didn't find any documentation for fold_convert - except the code. In general, the fold_foo functions try to do foo, simplifying away useless operations. So fold_convert adds a type conversion, unless that is unnecessary (if the types are already the same for example). Mikael
